Intramammary benign vascular proliferative lesions on MRI during neoadjuvant chemoimmunotherapy with camrelizumab in TNBC patients.

[PURPOSE] Reactive cutaneous capillary endothelial proliferation (RCCEP) is a common immune-related adverse event (irAE) associated with camrelizumab. We aimed to explore and describe benign vascular proliferative lesions occurring within breast tissue of triple-negative breast cancer (TNBC) patients undergoing neoadjuvant chemoimmunotherapy (NACI) with camrelizumab.

[METHODS] We conducted a retrospective single-center analysis of 106 TNBC patients treated between March 2021 and August 2023 (mean age 48.1 ± 11.2 years). The cohort included 60 patients receiving neoadjuvant chemotherapy (NAC) and 46 patients who underwent NACI with camrelizumab. Clinical data, pathological characteristics, and MRI findings at baseline and during each treatment cycle were analyzed for all participants. Post-treatment newly identified abnormal lesions within breast tissue were detected and characterized.

[RESULTS] Abnormal enhancement was observed in 30 patients (3 NAC vs. 27 NACI, P < 0.001). In the NACI group, abnormal enhancement included 3 cases of ring enhancement (3/27, 11.1 %), 2 cases of linear enhancement (2/27, 7.4 %), and 22 cases of mass enhancement (22/27, 81.5 %). These lesions typically emerged after the second treatment cycle, with few appearing after the fourth or sixth cycle. Most lesions (26/27, 96.3 %) regressed with continued treatment. In the NACI group, the development of new enhancement lesions was correlated with younger age (P = 0.007), premenopausal status (P = 0.014), a lack of peritumoral edema on baseline MRI (P = 0.007), and the presence of mass enhancements (P = 0.012).

[CONCLUSION] TNBC patients treated with camrelizumab frequently develop benign vascular proliferative lesions in the breast tissue, primarily manifesting as mass enhancements on MRI that typically regress with continued treatment without requiring therapy discontinuation.